DOKK / manpages / debian 10 / tk8.6-doc / Tk_DeleteEventHandler.3tk.en
Tk_CreateEventHandler(3tk) Tk Library Procedures Tk_CreateEventHandler(3tk) 







Tk_CreateEventHandler, Tk_DeleteEventHandler - associate procedure
    callback with an X event








#include <tk.h>

Tk_CreateEventHandler(tkwin, mask, proc, clientData)

Tk_DeleteEventHandler(tkwin, mask, proc, clientData)









  
Tk_Window tkwin (in)

  
Token for window in which events may occur.

  
unsigned long mask (in)

  
Bit-mask of events (such as ButtonPressMask) for which proc
      should be called.

  
Tk_EventProc *proc (in)

  
Procedure to invoke whenever an event in mask occurs in the window
      given by tkwin.

  
ClientData clientData (in)

  
Arbitrary one-word value to pass to proc.
    
    

    

  










Tk_CreateEventHandler arranges for proc to be
    invoked in the future whenever one of the event types specified by
    mask occurs in the window specified by tkwin. The callback to
    proc will be made by Tk_HandleEvent; this mechanism only works
    in programs that dispatch events through Tk_HandleEvent (or through
    other Tk procedures that call Tk_HandleEvent, such as
    Tk_DoOneEvent or Tk_MainLoop).


Proc should have arguments and result that match the type
    Tk_EventProc:




typedef void Tk_EventProc(


        ClientData clientData,


        XEvent *eventPtr);



The clientData parameter to proc is a copy of the
  clientData argument given to Tk_CreateEventHandler when the
  callback was created. Typically, clientData points to a data structure
  containing application-specific information about the window in which the
  event occurred. EventPtr is a pointer to the X event, which will be one
  of the ones specified in the mask argument to
  Tk_CreateEventHandler.

Tk_DeleteEventHandler may be called to delete a
    previously-created event handler: it deletes the first handler it finds that
    is associated with tkwin and matches the mask, proc,
    and clientData arguments. If no such handler exists, then
    Tk_HandleEvent returns without doing anything. Although Tk supports
    it, it's probably a bad idea to have more than one callback with the same
    mask, proc, and clientData arguments. When a window is
    deleted all of its handlers will be deleted automatically; in this case
    there is no need to call Tk_DeleteEventHandler.


If multiple handlers are declared for the same type of X event on
    the same window, then the handlers will be invoked in the order they were
    created.








bind, callback, event, handler







  

    
    Tk